Telephone system



Feb. l, 193% F. WOLF TELEPHONE SYSTEM Filed Feb. 10, 1956 2 Sheets-Sheet l INVENTOR. FRITZ WOLF ATTORNEY.

Feb. 1, 1938.

F. WOLF TELEPHONE SYSTEM Filed Feb. 10, 1956 2 Sheets-Sheet 2 TSt.2

ATTORNEY.

Patented Feb. 1, 1938 UNITED STATES PATENT OFFICE TELEPHONE SYSTEM Germany Application February 10, 1936, Serial No. 63,114 In Germany February 2-7, 1935 8 Claims.

This invention relates to a circuit arrangement for remote communication systems and more especially for telephone systems in which a plurality of lines extending in various traiiic directions are in connection with a plurality of connecting paths by way of a common connecting line, leading to an exchange and a junction point in the latter. In the case of outgoing calls undesired switching-over operations in the connecting devices of the exchange, caused by the speaking path to the calling subscribers line not being completely established in due time, are prevented, and at the same time an efficient impulse transmission is ensured, in that a potential which is connected up under the influence of a call initiating impulse, and serves to influence controlling means in the connecting devices, is disconnected after the call has been initiated in the exchange but not before the speaking line has been switched through to the calling line.

The present invention is concerned with means for preventing disturbances in operation by influencing the controlling means in connecting devices of an incoming connecting path, while maintaining efiicient impulse transmission in the case of outgoing calls. This is accomplished according to the invention in that an auxiliary potential is applied to the connecting path of a line which is to be used in a speaking connection and which is connected to the exchange by way of a connecting line common to other subscribers lines, for the purpose of influencing controlling means (feeding bridges) in connecting devices in the exchange transitcrily in the case of outgoing calls and in the case of incoming calls throughout the duration of the latter.

By means of the arrangement according to the invention it is possible for this principle, which renders efiicient impulse transmission possible in the case of outgoing calls and consists in connecting up an auxiliary potential only transitorily in the case of outgoing calls, also to be used in systems in which the called subscriber can take up and replace his receiver a number of times. 45 On account of the auxiliary potential being connected throughout the duration of the incoming call, the influencing of the feeding bridge in the incoming connecting path, which occurs when the receiver is replaced again after having been taken up and causes undesirable switching operations, is

effectively prevented.

In the embodiment so-called two-party line systems are shown in which two subscribers stations Whose lines are brought together at a switching point are connected to a switching-over point (UStZ) by way of a common connecting line. The invention is, however, not limited to two-party line systems. It is also possible for more than two subscribers lines to be associated at the switching-over point UStl, and also in place of subscribers stations, connecting lines, party lines or the like may be connected up.

In the drawings, Fig. 1 shows an arrangement of the invention, while Fig. 2 shows a modification thereof.

In the embodiments two subscribers stations TStl and 'IStZ are shown whose lines are connected to the switching-over point UStZ to the exchange devices in which an individual approach to preselecting devices (preselectors or call finders) is provided for each subscribers station of the two-party line. Intercommunication between the two subscribers of the two-party line is not possible.

The manner of operation of the arrangement according to Fig. 1 is as follows: If a subscriber, for example, the subscriber at station TStl wishes to set up a call he takes up his receiver and thereby closes the circuit for relay RI in the switchingover point UStZ: earth, battery, winding I of relay RI contact ltl, contact 2152, a-lead of the connecting line, winding I of relay Ul, contact 3u2 line to subscribers station TStl, contact 411,2, winding 11 of relay Ui, contact 5ul, earth. Relay III which is situated in this circuit does not energize. Relay R! is energized, however, at the switching-over point UStZ and by closing its contact 6H connects earth to the a-lead over contact 1H, while over contact 81"! battery through chokecoil Dr! is connected to the b-lead. The preselector W! is accordingly set in motion in known manner. When it finds a free group selector GW relay T in the preselector is energized in the known manner and switches through the line to the group selector over contacts 9t and Hit. Relay T! at the switching-over point UStZ is accordingly energized over the circuit: earth, battery in the group selector, a-lead, preselector VWl, contact 9t, winding I of relay Tl, contacts 61'! and it! and earth. Relay '1'! looks up over contact Hi! and resistance W2! and its winding II. Blocking potential is connected to the final selector approach of the second subscriber over contact l5tl so that this is protected against incoming calls. Moreover, the opening of contact lZtl and the closing of contact ittl effects the switching-over of the junction at the switchingover point USt2. By the closing of contact Hit! the battery potential connected to the a-lead in the group selector G-W operates directly on relay III at the switching-over point UStI. Relay Ui is accordingly energized and opens its contact MI and closes its contact I5uI so that the speaking path is switched through at the switchingover point UStI.

Meanwhile, the slow operating relay RI has finally released at the switching-over point UStZ and by closing contact I6rI has switched through the b-lead of the speaking line to the group selector in a metallic circuit while shunting con denser CI. Since contacts SH, SH, IIrI, and I8rl are now open there are now no switching means associated with the speaking path which are capable of distorting the impulses.

Corresponding operations are brought about when a call is initiated from the subscribers station TStZ. While a call is in progress from one subscribers station the other subscribers station is completely disconnected from the connecting line on account of the opening of contacts 3112 and M2 or ISuI and 20m.

In the case of incoming calls, for example to subscriber T StI, a circuit is established for relays RI and TI after the final selector has tested on the appropriate contact: earth in the final selector LW, c-lead, winding II of relay RI contact 2H2, winding II of relay TI, battery, and earth. Relays RI and TI energize in this circuit. By closing contact I4tI relay TI switches through the a-lead of the speaking line while the switching-over of the junction is effected by the closing of contact I 3tl. In order to prevent undesired switching operations from being brought about in the preceding selecting device GW if, in contrast to the conditions obtaining in the case of individual subscribers outgoing calls, wherein the loop is not immediately closed when the subscriber calls, because the switching over device on switching over points UStI and UStZ must first be operated, an auxiliary potential is applied to the b-lead of the connecting. line over contact 8rI: earth, battery, choke coil DrI, contact 8rI, b-lead to the final selector. By this means, the criterion for toll knock down is prevented from being produced in preceding selecting devices GW. This auxiliary potentialremains operative throughout the duration of the incoming call. For the purpose of balancing the subscribers line a choke coil D12 is connected over contact I'IrI, while over 22M and the choke coil D13 earth potential is applied to the b-lead of the connecting line leading to the switchingover point UStI. When the called subscriber replies relay UI energizes over the earth applied by way of contact 51d and locks up after closing its contact I5uI over contact 2211 and the choke coil Dr3.

On the release of the connection relays UI and RI deenergize on account of the release of the final selector LW. Moreover, relay T in the preselector is connected in parallel with the relay TI (winding II) so that this also returns to its rest position and the switching-over devices are accordingly restored to normal.

The second embodiment is differentiated from the first only in the construction of the switching over point USt2, the difference being in the arrangement of the bridge for connecting the auxiliary potential which in this case consists only of the choke coils DrI, Dr! or Dr3, Dr l. The b-lead of the speaking line is permanently switched through at the switching-over point Ust2 in a metallic circuit; On initiating an outgoing call auxiliary potential is connected to the b-lead of the line over contact Srl and the choke coil DrI on the energizing of relay RI, as in Fig. 1, and remains connected up until relay RI releases when the speaking path is finally switched through to the calling line.

In the case of incoming calls relays RI and TI- are energized over winding II, as in Fig. 1. Over contact 8rI relay RI connects auxiliary potential to the b-lead and thus prevents the transmission of the criterion for toll knock down. In place of a second winding of relay RI a special auxiliary relay I-II can be provided which connects the auxiliary potential to the b-lead over its contact hI and the choke coil DrI. The further switching operations correspond to those in Fig. 1.

In order to ensure the energizing of relay TI, winding II of this relay can in the case of outgoing calls be connected over resistance WiI and contact 2211 so that it is pre-magnetized without being energized. When the switching through to the group selector GW takes place only a small amount of energy is necessary to cause the relay TI to energize over its winding I. Also in the case of incoming calls the energizing of relay TI can be ensured in a special manner if a third low resistance winding is provided in the incoming c-lead in series with winding II, this facilitating the energizing of relay TI over its winding II.

What is claimed is:

1. In a telephone system, a. common line, telephone lines branched from one end of said common line, connecting lines branched from the other end of said common line, switches in each connecting line for extending calls from said telephone lines, means responsive to an incoming call over either connecting line or an outgoing call on one of said telephone lines for taking said common line and one of said connecting lines into use to the exclusion of the other telephone line and connecting line, switching means in said connecting line operated responsive to the call to apply an auxiliary potential to the connecting line to influence the switches thereon, said switching means operated transitorily responsive to an outgoing call and for the duration of an incoming call.

2. In a telephone system, a common line, a. pair of telephone lines branched from one end of said common line, a pair of connecting lines corresponding to said telephone lines branched from the other end of said common line, switches in each of said connecting lines for extending calls, means responsive to an incoming call or an outgoing call for taking the common line and one of the connecting lines into use to the exclusion of the other telephone line and connecting line, a relay in the connecting path taken into use, said relay operated momentarily in the case of an outgoing call and continuously in the case of an incoming call, and means controlled by the opera tion of said relay for applying a particular potential to the connecting line in order to control the operation of the switches on the connecting line.

3. In a telephone system as claimed in claim 2 in which the switching through of the connecting line the common line and the telephone line in a loop circuit to the associated switches is interrupted transitorily by the relay responsive to an outgoing call and responsive to an incoming call for the duration of the same.

4. In a telephone system as claimed in claim 2 in which the common line telephone line and connecting line are switched through in a loop circuit to the associated switches and in which the relay connects the auxiliary potential transitorily to the line in the case of outgoing calls and. for the duration of an incoming call, and in which in the case of the incoming call the auxiliary potential and the breaking of the loop circuit to the switches takes place at the time when the connecting line corresponding to the wanted telephone line is engaged.

5. In a telephone system, a common line, a pair of telephone lines branched from one end of said common line, a pair of connecting lines branched from the other end of said common line, switches in each of said connecting lines for extending calls, means responsive to a call for taking one of said telephone lines the associated connecting line and the common line intouse, said lines adapted to be switched through in a loop circuit to the associated switches, a relay in the connecting line operated transitorily responsive to an outgoing call and for the duration of an incoming call, said relay connecting an auxiliary potential to the connecting line and interrupting the loop circuit extending to the switches in order to effect a control of the same, said relay operated in the case of an incoming call over the testing circuit for the connecting line and in the case of an outgoing call over one side of the connecting and telephone lines.

6. In a telephone system as claimed in claim 5 in which the other telephone line and the other connecting line are disconnected from the common line when the first telephone and connecting lines are engaged in a call, and in which said other telephone and connecting line is guarded from seizure on an incoming call while said first lines are in use.

'7. In a telephone system as claimed in claim 5 in which a further auxiliary potential is applied by the relay to one side of the connecting line responsive to an outgoing call in order to initiate the operation of the switches, and in which the said further auxiliary potential is disconnected by an auxiliary relay operated responsive to an incoming call.

8. In a telephone system as claimed in claim 5 in which a further potential is applied by the relay to one side of the connecting line responsive to an outgoing call in order to initiate the operation of the switches, and in which the said further auxiliary potential is disconnected by an auxiliary relay operated responsive to an incoming call, said auxiliary relay operated over the incoming testing circuit simultaneously with said first relay.

FRITZ WOLF. 

